The primary emphasis of the work will center around the study of acuity and color vision in human infants. Acuity is being measured as a function of the orientation of gratings, at several illuminance levels, in infants from 0 to 6 months of age. The techniques used will be preferential looking and tracking. Photopic and scotopic spectral sensitivity curves and the presence or absence of trichromacy will also be determined by the tracking technique. Work with infant monkeys will also be supported during the first six months of the grant. Color vision studies will be continued, and acuity studies will be begun. Psychophysical studies of adult human vision will be continued. Difference thresholds between two supra-threshold spots of light will be determined, as a function of their illuminance level and the adaptation level of the subject. The results will be compared to predictions made from Werblin's model of light and dark adaptation processes in vertebrate retinas.